Title

Rotor Efficiency

Problem Scenario

Seeing if the addition of propellers affects the volts created.

Broad Question

What is the most efficient rotor design?

Specific Question

Does the number of blades affect the rotor efficiency?

Hypothesis

The rotor with more blades will be more efficient than the rotor with less blades.

Graph of Hypothesis

Variables

Independent Variable:

number of blades.

Dependent Variable:

rotor efficiency

Variables That Need To Be Controlled:

1.) The [[#|wind]] speed needs to be controlled so that during one of the tests the fan isn't blowing faster
2.) The rotor blades need to all have the same dimensions so that one doesnt catch

Vocabulary List That Needs Explanation

Volt- The SI unit of electromotive force, the difference of potential that would carry one ampere of current against one ohm resistance.
Rotor- A rotary part of a machine or vehicle, in particular.

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General Plan

I will attach a different number rotor blades to a battery motor that will have a volt meter and a lab quest attached to it. Then once I have attached the appropriate amount of blades I will turn on the fan and will collect the data for aproximently one minute to find the average amount of volts to find the most efficient number rotor blades.

Potential Problems And Solutions

A potential problem is that when the fan blows on the propellers they won't spin and create the volts needed to conduct the experiment. To keep this from happening I can bend the blades so that when the fan blows the air will catch the sides of the blades and will rotate them. Another potential problem is that while collecting the data the propellers could spin faster at different times. A way to solve this problem would be to conduct the experiment for one minute then I will use the average number of volts. Also a potential problem could be that the fan could blow the propellers faster in some spots. The way to solve this problem would be to put the motor up the same spot on the fan every time through out the experiment to make sure the data is consistent.

Safety Or Environmental Concerns

A safety issue that could possibly electrocute myself while conducting my experiment so to avoid this possible safety concern I could find a place to hold the motor where this wouldn't and couldn't happen. Another safety concern is that while hooking the volt meter onto the motor it clips onto my finger and cuts it and causes me to start bleeding the way to solve this is to keep my hand away from the hook so that it isn't near my finger so it wouldn't be able to clip onto my finger.

Experimental Design

What is your experimental unit?

two rotor blades

Number Of Trials:

four trials

Number Of Subjects In Each trial:

one

Number of Observations:

one

When data will be collected

February 25-27

Where will data be collected?:

the data will be collected in the team one science room in kennett middle [[#|school]].
(add the correct headings from the experimental design page before beginning)

Resources and Budget Table

Item	Number needed	Where I will get this	Cost
battery motor	1	Mr. Littlefield	$0
volt meter	1	Mr. Littlefield	$0
plastic rotor blades	8	me	$0
fan	1	Mr. Littlefield	$0

Detailed Procedure

I will construct eight rotor blades out of plastic that will all have the same dimensions. Next I will attach the rotors(two, four, six, or eight depending on the part of the experiment) to the the top of the battery motor using scotch tape. Then I will attach the voltmeter that will be plugged into the lab quest which will collect the data on to the battery motor so I will be able to see the total number of volts the different number of rotors create. Finally before I turn the fan on and start to turn the rotor and start generating the volts I must bend all of the attached propellers so that the wind from the fan is able to spin the rotor and I am able to conduct the experiment for all four variations of my experiment. While collecting the data the experiment will run for a total of one minute.

Diagram

Photo List

Time Line

2/23 experiment done
3/1 analysis done
3/7 discussion done
3/15 poster done

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Data Table

number of blades	Average number of volts
2	0.041
4	0.042
6	0.042
8	0.043

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Data Analysis

All Raw Data

See data table

Graphs

Photos

Results

As seen in the graphs and dat table the more rotor blades is the most efficient in creating volts. It may not be be by a lot but the eight rotor blades is the most efficient with an average of 0.043 volts generated. While the six blades and the four blades are tied for second place with an average of 0.042 volts generated. The two rotor blades was the least efficient with an average of 0.041 volts generated in the minute of collecting the data. These results are really close together so its hard to say that any of them was way more efficient than any of the others but from the data collected eight blades is the most efficient.

Conclusion

The rotor with more blades will be more efficient than the rotor with less blades. The conclusion is that yes the number of rotor blades does affect the efficiency of volts created by the rotor. In the experiment it was found that having a larger number of rotor blades is more efficient than a smaller number of blades. We can see this from the data how when the motor had the eight blades on it it created the most volts when it created an average of 0.043 while when the motor had only two blades attached to it, it only created an average of 0.041 which was the smallest average of them all. So this proves that my hypothesis was correct that the more blades you have the rotor will be more efficient than a rotor with less blades.

Discussion

In the experiment the independent and the dependent variables have a strong relationship. This relationship is seen on the graph by the smallest number on rotor blades being two creates the smallest number of volts which was 0.041 while the two middle rotor blades which were four and six created the middle number of volts 0.042 and the biggest number blades eight created the largest number of volts 0.043. This shows that the the two variables have a strong relationship because the smallest number of blades created the smallest number of volts and the biggest number of blades created the largest number of volts. From the experiment I was able to answer the specific question which was does the number of blades affect the rotor efficiency? The answer to this question was yes the number of blades does affect how efficient the rotor is, the more blades the more efficient.Ways this experiment could be improved is the rotor blades could be made out of a less flimsy material so they don't bend while the fan is blowing also they could be attached with something stronger than scotch tape so they are held down better during the test. Also another thing that could be changed to further the experiment is that the scale of the blades could be increased and the wind source could be stronger to spin it faster to see if the wind speed affects the efficiency of the rotor. To further this experiment even more another variation could be that the shape of the rotor blades to see if the shape is what makes a rotor more efficient. During the experiment there were a couple problems that were encountered, one was that the hooks that the volt meter hooks on to broke off which made things way more complicated than they should have been. The other problem was that in the beginning the blades wouldn't turn. All of these problems were solved or there was a way to still conduct the experiment without fixing the problem. Even though there were problems during the experiment all of the data that was collected is correct.

Benefit to Community and/or Science

This experiment could be very important because it could help people who design rotor systems for helicopters and wind turbines to try to create the most efficient rotor.

Background Research

In case some don't know what a rotor is, first you have to understand is that there are many different kinds of rotors in some cases a rotor can be used as a mathematical term or it can be a part of a car brake but for the experiment the rotor used resembles a helicopter rotor the closest. To relate the project to the helicopter rotor the number of blades on a helicopter rotor depends on the size of the helicopter, the smaller the helicopter the less blades needed and the bigger the more blades needed. The helicopter rotor which depends on lift to get the helicopter off the ground and lift is calculated by the Lift Equation: (Lift= coefficient x density x velocity squared x wing area) the wing area is the blades and the more blades the more surface area which ultimately causes more lift so for the helicopters rotor it is more efficient with more blades on it rather than a smaller number. The most important factor for a rotor design is the lift to drag ratio, the ratio should be as high as possible. There are two kinds of rotor blades they are symmetrical aerofoil and asymmetrical aerofoil most blades used to be symmetrical aerofoil's but it is possible to get a higher L/D ratio using a asymmetrical aerofoil. When the blades on a rotor rotate every part of the blade is traveling at a different speed. On the blade the velocity is greater the further you get away from the root this results in the distribution of lift to differ on every point on the blade. Some ways that the distribution can be fixed is with twist and sometimes tapered. Twisting the blade is that the angle of attack increases going towards the root which creates more lift. Tapering the blades makes the surface area larger as you get closer to the root this makes the distribution of lift more even through out the blade.

References

"Rotor Blade Design." Rotor Blade Design. N.p., n.d. Web. 24 Mar. 2013.

"The Lift Equation." The Lift Equation. N.p., n.d. Web. 24 Mar. 2013.

"Helicopter Rotor." Wikipedia. Wikimedia Foundation, 24 Mar. 2013. Web. 24 Mar. 2013.

Abstract

In the beginning I came up with the idea to test the efficiency of a rotor because I am interested in how helicopters and aerodynamics. First I came up with the broad question "what is the most efficient rotor design?" then I came up with the specific question "Does the number of blades affect the rotor efficiency?". After the question was developed I created my hypothesis which was the rotor with more blades will be more efficient than the rotor with less blades then I started planning my experiment. next after the planning was done it was time to conduct the experiment by doing testing the eight different number of rotor blades. After the experiment was complete and the data was collected I created the graph and data table which allowed to complete the data analysis. Finally after finishing the data analysis I was able to write my abstract and finish my wiki page by completing the wiki page I was able to make my poster and finish my science fair project and am ready to present my project.